1. Field of the Invention
The present invention pertains to a flow cell for analyzing fluid samples using a spectrophotometer type analyzer and light transmitting probes which are mounted in the cell to permit some light absorbance by the sample fluid.
2. Background
The development of improved optical fiber type transmission members and fittings has provided for improved chemical and refinery process control using spectrophoto-meter type process analyzers. For example, in the refining of petroleum fuels, there has recently been developed an on-line gasoline octane monitoring system using a process spectrophoto-meter, together with fiber optic waveguides to transmit "light" signals between the instrument and the process stream. A sample flow cell and probe arrangement monitors a sample flowstream of the gasoline blend whereby a "light" beam or signal in the ultra violet-visible light-near infrared (UV/Vis/NIR) portion of the spectrum is passed through the gasoline sample flowstream and the gasoline selectively absorbs some near infrared components of the light beam based on its specific chemical composition. The strength of this absorption phenomena can then be related to the sample octane number, for example.
However, one problem with sample probes for spectrophotometers which monitor radiation in the UV/Vis/NIR portion of the spectrum is that the spacing between the light signal transmitting probe members or the so-called sample path length is not adequately controlled. Since the amount of light absorption is proportional to the path length of light passing through the sample being analyzed, the spacing of the path length or the distance between the light transmitting members of the probe/waveguide circuit must be closely controlled. Known types of sample probes do not provide this important feature in a manner which has been deemed suitable.
Another problem associated with known probes of the general type discussed herein pertains to the tendency of the waveguides to become clouded or dirty in use. However, the present invention overcomes some of the deficiencies of known types of sample flow cell/probe arrangements for spectrophotometer type process or sample analyzers, including those mentioned herein.